my bike lost mph

I was on my bike going 100mph and cars started passing me cause I couldn't go any faster. my 750 suddenly lost mph, I can only accelerate to 100mph. My water, oil are good, and my oil filter, i just changed it. Have you ever herd of this problem? should i get a tune-up it has 45k miles on it, it might be a engine problem maybe.

I was doing a night ride, I think they where trying to keep up with me.
my 03 gixxer was going 160mph no problem, now I can tell there is a problem when changing gears, I have to gear up fast to 3-4 to go 40mph it seems. Before I could max my rpm in 2nd and go that fast, but now i can't. Is there too much air going in the engine?